1. Field of the Invention
The present invention relates generally to fence gates and similar closure apparatus, and more particularly to a novel bifold closure super-structure and apparatus having on-board electromechanical drive apparatus for moving a closure between its open and closed positions.
2. Discussion of the Prior Art
Heretofore, fence gates and large closure doors have either been of the swinging type, wherein either one or two panels are pivotly connected to side posts and rotated at least 90.degree. degrees from a closed position to an open position, or of the sliding type in which one or more panels is mounted on a track or on rollers of one configuration or another and slideably moved between a closed position and an open position.
The problem with the former configuration is that it requires the swinging of a rather large gate unit, or pair of gate units, and requires a correspondingly large free ground surface area over which the gate unit(s) may be rotated and parked. In addition, if the gate(s) must be opened outwardly, sufficient room for an incoming vehicle must be provided. Whereas this configuration may be suitable for some applications in which space is available, there are certain applications to which such a gate cannot be used, or is impractical for use due to limited space, sloping ground surface, etc.
For many applications in which the swinging gate configuration is inappropriate, the sliding configuration can be used. In the case of a sliding gate, when moved into the open position the gate is merely "parked" beside an adjacent section of fence. This is in many situations a quite suitable arrangement, particularly when the gate is disposed at a point along the length of a long straight section of fence.
However, for those cases where it is not possible to provide room within which to swing or slide the gate panels, it may be possible that neither of the above types of gate can be utilized. For such situations it has been necessary to utilize other specialized, nonstandard configurations involving an overhead, rolling or guillotine type structure, or even a cantilevered, flag type of gate mounted similar to railroad type crossing barriers.
Another problem associated with swinging and sliding gates involves the mechanism required to accomplish automatic and/or remote actuation of the opening and closing operation. In swinging gates, a relatively long swinging arm is usually affixed to an actuating mechanism in a large black box positioned beside each gate unit. The actuating mechanism is typically some type of motor driven crank that in rotating the arm causes the gate unit to likewise be rotated from one position to the other.
In the case of the sliding gate, a similar large black box is used to drive a cable, chain, or rack and pinion mechanism for moving the gate along its opening/closing path.
Aside from the aesthetic interference of the "black boxes" with the overall appearance of the gate and fence combination, these devices normally require costly mounting pads, special electrical wiring and give rise to other undesirable requirements.
With regard to large openings requiring closures, such as aircraft hangers, warehouses, large garages, etc., similar problems are encountered, except that in many of these cases it is possible to use an overhead track mounted closure. However, there are other applications in which less than suitable closure carrying and actuating mechanisms must be utilized for want of better solutions.
Still another problem associated with many prior art gate and closure structures is that they do not provide adequate crash barrier protection suitable for limiting the intrusion of heavy vehicles bent upon penetrating the closure.
A similar disadvantage relating to concussion caused damage is found in many track mounted hanger doors; that is, a substantial shock or pressure wave may dislodge the door rollers from the track and render the door unopenable without disassembly, the use of jacks, etc.
A still further problem associated with prior art gating structures is the difficulty of providing incipient intrusion warning and avoidance features.